Since upgrading to Lion, iChat refuses to connect to either my AIM or Google Talk accounts. (Not a Google Apps account, fwiw.) Interestingly, if I sign in to AIM on another computer and try to get iChat to sign on, I get a message that I'm trying to sign on in more than one place, but iChat still shows status as "offline" for all accounts.

So far, I've tried deleting all the com.apple.iChat preferences in Library, but to no avail.